微波诱导Fe2O3/Al2O3催化剂催化氧化处理水中苯酚

 以γ-Al2O3为载体,采用浸渍-焙烧法制备了Fe2O3/Al2O3催化剂,并将其应用于微波诱导催化氧化处理模拟含酚废水. X射线衍射和X射线荧光光谱测试结果表明,活性组分氧化铁在催化剂中以α-Fe2O3的形式存在,其含量为3.71%. 与载体氧化铝相比,Fe2O3/Al2O3催化剂的比表面积和平均孔径及平均孔容略有降低. 对于100 mg/L的模拟含酚废水,最佳的处理工艺条件为: 微波辐照功率400 W,辐照时间5 min,催化剂加入量60 g/L,H2O2浓度600 mg/L,体系pH＞4. 在此工艺条件下,水中苯酚的去除率达97.98%. 催化剂连续使用20次后苯酚去除率仍达96.34%. 表观反应动力学研究表明,在氧化铁催化剂存在的条件下,微波诱导H2O2产生氧化性极强的羟基自由基,整个反应过程可分为微波诱导阶段和催化氧化阶段,两个阶段的氧化过程均符合一级反应动力学规律.     

微波辅助纳米CeO_2/H_2O_2体系催化氧化苯酚的研究

以Ce(NO3)3·6H2O和NH3·H2O为原料,采用沉淀法制备Ce O2粉体,采用X射线衍射仪、扫描电子显微镜对催化剂的晶相结构和表面形貌进行表征。在微波加热作用下,以苯酚为模拟含酚废水对催化剂的催化性能进行了测定,并探讨了原料投加量、搅拌时间、微波加热时间等对苯酚去除率的影响。结果表明:所制备的Ce O2纳米材料为高度结晶的立方萤石型结构,平均粒径为36.5 nm。在微波辅助Ce O2/H2O2体系催化降解苯酚实验中,当苯酚初始浓度500 mg·L-1,投加纳米Ce O20.4 g,10%H2O20.6 m L,室温下搅拌60 min,微波反应器中以100℃反应40 min,苯酚的去除率达到87%以上。     

纳米Fe2O3-K2O催化剂的制备及其催化乙苯脱氢性能

采用浸渍-热分解法制备了纳米Fe2O3-K2O催化剂,并在常压和520～580℃的条件下,考察了其对乙苯催化脱氢反应的催化性能.结果发现,纳米Fe2O3-K2O催化剂表现出很好的活性和稳定性.在550℃,N2/H2O/乙苯摩尔比为30.7/10/1和WHSV=0.43h-1的条件下,纳米Fe2O3-K2O催化乙苯脱氢的转化率为71.9%,苯乙烯选择性为91.1%.透射电子显微镜和X射线衍射测试结果表明,氧化铁的粒径为10～14nm.催化剂的尖晶石结构和高比表面积是其表现出高催化性能的主要原因.     

TS-1分子筛对固定床中苯酚羟基化反应的催化性能

 制备了用于固定床反应器的负载型TS－1分子筛催化剂,并以苯酚羟基化为探针反应,研究了载体、钛含量和预处理剂等对负载型TS－1分子筛催化性能的影响,考察了固定床反应器中苯酚羟基化反应的工艺条件．结果表明,酸性较强的载体会加剧H2O2的分解,导致苯酚的转化率和H2O2的有效利用率下降;在所研究的ZSM－5,TiO2,Al2O3,ZrO2,SiO2和硅藻土载体中,硅藻土具有最好的催化性能;催化剂的活性与骨架钛含量有关;用HNO3,KAc,NaAc,NH4Ac和NH4Cl处理过的催化剂,活性和选择性得到提高,而用NH3·H2O,Na2CO3和Na3PO4等碱性物质处理后,催化剂的活性则下降;溶剂、反应温度、原料空速和苯酚／H2O2摩尔比对苯酚羟基化反应有很大影响．以丙酮为溶剂,在苯酚／H2O2摩尔比为3,反应温度为84℃,WHSV为8．46h－1的反应条件下,苯酚转化率、H2O2转化率、苯二酚选择性以及H2O2的有效利用率可分别达到27．7％,94．8％,97．7％和75．1％．     

不同催化剂对苯酚H2O2羟基化反应的比较

用苯酚、双氧水经羟基化反应合成邻、对苯二酚,在Fe2O3为催化剂的反应系统中,反应诱导期长,且反应剧烈;当以杂多酸盐或Fe/ZrO2为催化剂时,诱导期消失,且羟基化反应平稳。 反应的诱导期可能是由铁的氧化物转化为活性物种Fe3+和Fe2+的过程引起的;在杂多酸盐或Fe/ZrO2催化剂的反应体系中,羟基化反应可能发生在催化剂表面而使反应变得缓慢平稳,反应诱导期消失。     

CeO2-La2O3/γ-Al2O3催化还原SO2反应机理的研究

 采用浸渍法制备了负载型CeO2/γ-Al2O3,La2O3/γ-Al2O3和CeO2-La2O3/γ-Al2O3催化剂,并用XRD和XPS对催化剂进行了表征,在n(SO2)/n(CO)=1/3,载流气体为N2,气体流量为1 L/min,催化剂用量为15 g的条件下,考察了催化剂催化CO还原SO2反应的性能,研究了催化剂的活化过程、催化活性和反应物配比对活性的影响. 结果表明,CeO2-La2O3/γ-Al2O3在催化还原SO2反应中的活化温度比单组分催化剂CeO2/γ-Al2O3或La2O3/γ-Al2O3下降了50~100 ℃,而且具有更高的活性. 这可以解释为由CeO2的redox反应与La2O3的COS中间物反应之间的协同作用所致. 还对SO2还原反应机理进行了探讨,发现CeO2的redox反应所生成的单质硫是整个过程中COS中间物反应的重要来源. 在此基础上,对CeO2-La2O3/γ-Al2O3催化CO还原SO2反应提出了redox-COS叠加反应机理.     

碳纳米管负载Co-Mo催化剂在孤岛减压渣油加氢裂化反应中的应用

采用等体积浸渍法制备了一系列不同Co/Mo原子比的碳纳米管（CNT）负载Co Mo催化剂。将该系列催化剂用于孤岛减压渣油加氢裂化反应，评价其催化效果，并在相同反应条件下与 γAl2O3负载Co-Mo催化剂的催化性能进行比较。结果表明，Co-Mo/CNT催化剂的催化效果略低于Co-Mo/γAl2O3催化剂。Co/Mo原子比对Co-Mo/CNT催化剂的催化效果有较大的影响。与相同载体的催化剂相比，当Co/Mo原子比为0.50时，Co-Mo/CNT催化剂具有最佳的催化效果，而Co-Mo/γAl2O3催化剂在Co/Mo原子比为0.35时具有最佳的催化效果。     

CeO2稳定Ru/γ-Al2O3湿空气氧化催化剂的研究

用CeO2作添加剂，对以γ-Al2O3为载体、RuO2为活性组成分的Ru/Al2O3湿空气氧化催化剂掺杂改性，用分步浸渍的方法制备出Ru/CeO2/Al2O3三元复合氧化物催化剂。经XRD分析，证明CeO2进入了γ-Al2O3的晶格，并且有效抑制了高温时γ-Al2O3向α-Al2O3的相变及RuO2向γ-Al2O3晶格的渗入，在270℃、5.5MPa条件下，对苯酚的催化氧化降解结果表明，CeO2的加入可明显提高催化剂活性，其中Ru:CeO2:Al2O3(质量比)=0.6：6：100的催化剂性能最佳，反应30min，苯酚的去除率为96.0％。     

Au/Fe2O3催化剂的制备及其对富氢气体中一氧化碳选择性氧化的催化性能

 采用共沉淀法制备了1.5%Au/Fe2O3催化剂,考察了加料方式对Au/Fe2O3催化剂化学组成及其催化富氢气体中CO选择性氧化性能的影响. 结果表明,正加法制备的Au/Fe2O3催化剂的性能明显好于反加法制备的催化剂,80 ℃时前者对富氢气体中CO选择性氧化反应的转化率为94%,CO2选择性为65%,连续反应10 h,催化剂活性没有变化. XRD,XPS和TEM等的测试结果表明,正加法制备的Au/Fe2O3催化剂中金粒子的平均粒径为2～4 nm,金粒子高度分散在载体上,并与载体之间发生了较强的相互作用,从而表现出较高的催化性能.     

Ag/Al2O3催化乙醇和甲醚选择性还原NOx反应机理的原位红外光谱研究

 尽管C2H5OH和CH3OCH3是同分异构体,但在以Ag/Al2O3为催化剂选择性催化还原NOx时,还原剂C2H5OH比CH3OCH3具有更高的活性. 原位漫反射红外光谱研究表明, C2H5OH和CH3OCH3在还原NOx反应过程中分别遵循不同的反应机理: 在Ag/Al2O3催化C2H5OH还原剂选择性还原NOx的反应过程中,烯醇式物种(RCH=CH-O-)和NO-3物种是主要的反应中间体,二者相互反应性能很强,可以生成反应关键中间体异氰酸酯(-NCO)表面吸附物种,因此NOx的去除率很高; 而在Ag/Al2O3催化CH3OCH3还原剂选择性还原NOx的反应过程中,甲酸盐(HCOO-)物种和NO-3物种是主要的反应中间体,二者之间反应生成-NCO 的活性较弱,因而NOx的去除率较低.     

Mechanism of Phenol Hydroxylation with Hydrogen Peroxide Catalyzed by Iron Complex Oxide

Dihydroxybenzene are both very important chemical products. The oxidation of phenol to produce catechol and hydroquinone has been researched extensively since the 1970s. In this paper, the iron complex oxide was prepared by the air oxidation of aqueous suspension method and the catalytic activities were investigated in the hydroxylation of phenol with H₂O₂ to catechol and hydroquinone. The results showed that the catalyst had higher catalytic activities and the phenol conversion could reach 24% when the phenol/H₂O₂ (mole ratio) was 3 and the catechol/hydroquinone (mole ratio) 1.5 in products. Furthermore, the interaction of the catalyst with H₂O₂ had also been demonstrated by IR spectrometry. In the presence of H₂O₂ a band at 956 cm^-1 appeared and disappeared when the H₂O₂ is replaced by H20 or the catalyst was heated over 373 K, at which temperature decomposition of iron peroxide was very likely. The band at 956 cm^-1 was due to the formation of structure of iron peroxide species and the stretching vibration of surface 0-0 species. The results of IR studies suggested that the catalyst might be react with hydrogen peroxide to form iron peroxide, which decomposed to produce·OOH radical. In the presence of DMPO (5,5-dimethyl-1-pyrroline-N-oxide) the·OH radical was also successfully captured in the hydroxylation of phenol by H₂O₂ over iron complex oxide catalyst in the first time that has been confirmed by means of ESR spectrometry. The results of ESR suggested the process of hydroxylation of phenol with H₂O₂ was probably a radical process. A possible mechanism of the catalytic process was proposed.     

Synthese et caractérisation de catalyseurs a base de cuivre: application a la réaction d'oxydation du phénol

Synthesis and characterization of copper catalysts: application to the oxidation of phenol. The catalytic oxidatin of organic pollution has already been treated several publications reporting the use of ozone, air or hydrogen peroxide as oxidants. These systems require very severe conditions of temperature and pressure. It was thus useful to develop active, stable and inexpensive oxidizing systems. For this purpose we prepared catalysts by impregnation of copper on a natural clay; these catalysts were characterized, then used in the reaction of oxidation of phenol in the presence of hydrogen peroxide, at atmospheric temperature and pressure. The results showed a very significant activation of hydrogen peroxide by the catalyst, the phenol depletion percentage reaching 65 % after 4 h, and very significant stability of the catalyst.     

Pd–Fe/TiO2 catalysts for phenol degradation with in situ generated H2O2

This study deals with the degradation of phenol over Pd–Fe/TiO₂ catalysts at mild conditions in the presence of in situ generated H₂O₂ from oxygen and formic acid. This catalytic system demonstrated interesting ability to oxidize phenol by Fenton process in a one-pot reaction without the addition of ferrous ion. Lower Pd content catalysts, despite producing a higher hydrogen peroxide amount for bulk purposes, did not reach the same efficiency as the 5Pd–5Fe catalyst in phenol degradation. A close interaction between Pd and iron oxide species is necessary to obtain high active catalysts. These results highlight the advantage of in situ generation of H₂O₂, for oxidation reactions with respect to conventional Fenton process.     

Selective oxidation of aromatic hydrocarbons by potassium and phosphorous-modified iron oxide–silica nanocomposite

Abstract  

Supported iron catalysts are active for hydrocarbon oxidation with H₂O₂, but the hydrogen peroxide dismutation is a shortcoming that may constrain their applications. Herein, we attempted to address this problem using potassium and phosphate-doped iron oxide–silica nanocomposite (KPFeSi) synthesized via sol–gel methods. The promoted silica–iron oxide nanocomposite has been characterized by elemental analyses, FTIR, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface-size determination. The synthesized KPFeSi was an active catalyst in the low-temperature liquid phase oxidation of various alkyl aromatics with hydrogen peroxide in conversions of 31–78%. Furthermore, the direct oxidation of benzene into phenol using hydrogen peroxide has been achieved in the absence of any acid with this KPFeSi compound.     

ZnFe0.25Al1.75O4催化剂在苯酚催化湿式氧化中的活性和稳定性

利用溶胶-凝胶法制备了ZnFe0.25Al1.75O4尖晶石复合氧化物催化剂,并将其用于苯酚催化湿式氧化反应.结果表明,这种催化剂对苯酚降解有较好的催化活性和稳定性.连续反应5次后,苯酚转化率为100%,COD去除率为88.7%.反应过程中,铁离子的溶出量先增加后减小,最终的出水金属离子浓度很低.第5次反应后的出水铁离子浓度为2.15 mg/L,锌离子浓度为1.53 mg/L.     

磷钨酸季铵盐催化氧化汽油深度脱硫

以十六烷基三甲基溴化铵和磷钨酸为原料制备了磷钨酸季铵盐催化剂,并对催化剂进行了红外光谱和SEM表征。研究了磷钨酸季铵盐为催化剂,双氧水为氧化剂,催化氧化法生产低硫汽油技术。考察了萃取剂以及氧化条件和萃取条件对脱硫效果的影响。结果表明,在汽油10 mL,双氧水0.01 mL,催化剂0.0016 g,氧化温度30℃,氧化时间60 m in的条件下,采用复合溶剂LJ-1进行萃取,萃取温度20℃,静置时间15 m in,剂油比为1时,直溜汽油中的硫含量由179.3 mg/L降至10.8 mg/L,脱硫率达94.0%。氧化萃取时的脱硫率比未经氧化直接萃取时的脱硫率高45.6%,氧化脱硫效果显著。     

Fe-K/AC催化氧化脱硫剂制备及反应机理研究

采用正交实验法制备了负载铁、钾的活性炭(Fe-K/AC)热煤气催化氧化脱硫剂,考察了活性组分铁、钾含量、二价铁和三价铁比例、煅烧温度对催化氧化脱硫反应活性的影响。由正交实验极差分析可知,各因素影响程度依次为:钾含量>铁含量>煅烧温度> Fe²⁺/Fe³⁺,最优制备条件为,铁含量0.5%、钾含量5.0%、煅烧温度600 ℃、Fe²⁺/Fe³⁺比0.5。通过对脱硫剂的孔隙结构和表面形貌分析可知,活性炭表面负载的铁金属氧化物具有催化氧化硫化氢生成单质硫的活性,碱金属氧化物具有协同作用,可以改变表面酸碱性,促进硫化氢的催化转化,但过高的金属氧化物负载量会阻塞孔道,减小反应比表面积,从而降低脱硫剂的反应活性。     

CeO2掺杂RuO2/γ-Al2O3催化剂结构与湿式氧化降解苯酚的活性研究

采用浸渍法制备了RuO2/γ-Al2O3和RuO2-CeO2/γ-Al2O3催化剂,利用XRD,XPS和ESR分析了催化剂的结构,并研究了湿式氧化降解苯酚的活性.结果表明,两种催化剂表面RuO2均有良好的分散性,并且催化剂表面存在氧空位和化学吸附氧,CeO2的掺杂使催化剂表面氧空位和化学吸附氧数量增加.两种催化剂对湿式氧化降解苯酚具有良好的催化活性,当苯酚质量浓度为4200mg/L,在150℃和3MPa下,RuO2/γ-Al2O3催化剂湿式氧化降解苯酚反应150min后,苯酚全部被去除,RuO2-CeO2/γ-Al2O3催化剂反应60min后,苯酚的去除率为96%.     

苯直接羟基化制苯酚研究进展*

综述了苯直接羟基化制苯酚的几种催化反应,包括阳极氧化法、N₂O氧化法、H₂O₂氧化法、O₂直接氧化法,这些反应均具有良好的原子经济性和环境效益.同时重点介绍了相关的催化剂及其活性中心,探讨了这些新型方法的工业应用前景.     

Selective oxidation of sulfide catalyzed by peroxotungstate immobilized on ionic liquid-modified silica with aqueous hydrogen peroxide

Two kinds of catalysts of peroxotungstates immobilized on ionic liquid-modified silica have been synthesized and characterized. By comparing with other heterogeneous catalysts, the most characteristic of these heterogeneous catalysts is the catalyst formed from the combination of catalytic active center peroxotungstate with an ionic liquid. Thereinto, ionic liquid-modified supported catalysts provide the hydrophobic environment for organic reactions. We presume that the heterogeneous catalyst would display excellent catalytic ability depending on the additive effect of an ionic liquid and peroxotungstate. Their catalytic properties in oxidation of sulfides to sulfoxides and sulfones were investigated with 30% aqueous hydrogen peroxide at room temperature. These recoverable catalysts both exhibit high catalytic activities in the oxidation reaction of sulfoxides and provide excellent chemselectivities towards sulfur groups with unsaturated double bonds when the aqueous hydrogen peroxide was greatly in excess. The yields of methyl phenyl sulfoxide were still satisfied when the catalyst was reused for a sixth time.